Apparatus and methods for treating root canals of teeth

ABSTRACT

Apparatus and methods for endodontic treatment of teeth provide effective cleaning of organic material (such as pulp and diseased tissue) from the root canal system. In an embodiment, a compressor system generates high pressure liquid (e.g., water) that flows through an orifice to produce a high-velocity collimated jet of liquid. The high-velocity jet is directed toward a surface of a tooth, for example, an exposed dentinal surface, and impingement of the jet onto the surface generates an acoustic wave that propagates throughout the tooth. The acoustic wave effectively detaches organic material from dentinal surfaces and tubules. The detached organic material is flushed from the root canal system by the liquid jet and/or by additional irrigation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/628,500, filed Feb. 23, 2015, entitled “APPARATUS AND METHODS FORTREATING ROOT CANALS OF TEETH,” which is a continuation of U.S. patentapplication Ser. No. 14/304,737, filed Jun. 13, 2014, entitled“APPARATUS AND METHODS FOR TREATING ROOT CANALS OF TEETH,” which is acontinuation of U.S. patent application Ser. No. 11/737,710, filed Apr.19, 2007, entitled “APPARATUS AND METHODS FOR TREATING ROOT CANALS OFTEETH,” which claims the benefit under 35 U.S.C. § 119(e) of U.S.Provisional Patent Application No. 60/793,452, filed Apr. 20, 2006,entitled “APPARATUS AND METHODS FOR TREATING ROOT CANALS OF TEETH,” theentire contents of each of which is hereby incorporated by referenceherein.

BACKGROUND

Field of the Disclosure

The present disclosure generally relates to methods and apparatus forremoving organic matter from a body location and, more particularly, tomethods and apparatus for removing organic matter from a root canalsystem of a tooth.

Description of the Related Art

In conventional root canal procedures, an opening is drilled through thecrown of a diseased tooth, and endodontic files are inserted into theroot canal system to open the canal and remove organic material therein.The root canal is then filled with solid matter such as gutta percha,and the tooth is restored. However, this procedure will not remove allorganic material from all canal spaces. The action of the file duringthe process of opening the canal creates a smear layer of dentinalfilings and diseased organic material on the dentinal walls, which isextremely difficult to remove. The organic material and necrotic tissuethat remain in the canal spaces after completion of the procedure oftenresult in post-procedure complications such as infections.

SUMMARY

In an embodiment, an apparatus for removing organic material from a rootcanal of a tooth is provided. The apparatus may comprise a liquid jetassembly having a liquid pressurization portion which pressurizes aliquid and a liquid beam forming portion in fluid communication with thepressurization portion. The beam forming portion may comprise an orificethat receives the pressurized liquid. The orifice may be sized andshaped to convert the pressurized liquid into a high velocity collimatedbeam that produces an acoustic wave upon impact with a surface of thetooth. The energy of the wave may cause organic material within thecanal to be detached from the surrounding dentinal surface along alength of the canal. The length of the canal may extend at least to anapical portion of the tooth.

In another embodiment, a method of removing organic material that fillsa root canal of a tooth is provided. The method comprises propagating anacoustic wave through the tooth. The method may also comprise detachingorganic material filling the canal from the surrounding dentinal tissueusing energy of the acoustic wave.

In another embodiment, a method of removing organic material fromdentinal tubules which extend laterally from a root canal is provided.The method comprises introducing energy into a plurality of tubulesthrough dentinal tissue such that at least a portion of an odontoblasticprocess within the tubules is detached from surrounding dentinal tissueand released from the tubule.

In another embodiment, a method for removing organic material from aroot canal of a tooth is provided. The method comprises impacting dentinwith an energy beam of a sufficiently high level to cause cavitations influid within the root canal. The cavitations maybe caused at least atlocations in the root canal remote relative to the location of energyimpact such that organic material within the canal may be detached fromsurrounding dentinal tissue.

In another embodiment, a method of removing organic material from a rootcanal comprises directing a liquid jet into the pulp chamber of a tooththrough an opening in a side of the tooth at a substantial angle to thelong axis of a root canal.

In another embodiment, a method of removing organic material from a rootcanal using a high velocity liquid jet is provided. The method comprisesproviding a handpiece for directing the liquid jet and positioning acontact member of the handpiece against a tooth to be treated. Themethod may also comprise using a sensor to sense contact of the contactmember with the tooth. The method also may comprise activating theliquid jet only after the contact is sensed by the sensor.

In another embodiment, a method of removing organic material from atooth is provided. The method comprises using acoustic energy to detachorganic material from surrounding dentin within a plurality of rootcanals of a single tooth substantially simultaneously.

In another embodiment, an apparatus for removing organic material from aroot canal of a tooth is provided. The apparatus comprises an acousticenergy generator arranged to couple acoustic energy to a dentinalsurface of the tooth. The acoustic energy may be sufficient to causeorganic material in the tooth to be detached from surrounding dentin atlocations remote from the acoustic coupling surface.

In another embodiment, a method of removing organic material from a pulpcavity of a tooth is provided. The method comprises providing a liquidjet beam by passing liquid through an orifice. The method may alsocomprise using a positioning member to position the orifice relative toan opening into a pulp cavity of the tooth such that the jet beam passesthrough the opening.

For purposes of this summary, certain aspects, advantages, and novelfeatures of the invention are described herein. It is to be understoodthat not necessarily all such advantages may be achieved in accordancewith any particular embodiment of the invention. Thus, for example,those skilled in the art will recognize that the invention may beembodied or carried out in a manner that achieves one advantage or groupof advantages as taught herein without necessarily achieving otheradvantages as may be taught or suggested herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section view schematically illustrating a root canalsystem of a tooth.

FIG. 2 is a scanning electron microscope photograph of a dentinalsurface within a canal system in a tooth and shows numerous dentinaltubules on the dentinal surface.

FIG. 3 is a block diagram schematically illustrating an embodiment of acompressor system adapted to produce a high-velocity liquid jet.

FIGS. 4 and 4A are cross-section views schematically illustrating anembodiment of a handpiece that can be used to maneuver the high-velocityliquid jet.

FIG. 5A is cross-section view schematically illustrating a distal end ofan embodiment of a handpiece configured to deliver a high-velocityliquid jet.

FIG. 5B is a graph showing an example velocity profile of a coherentcollimated jet.

FIG. 6A is a cross-section view schematically showing an endodonticmethod in which a high-velocity jet is directed toward dentin through anopening in the top of a tooth.

FIG. 6B is a cross-section view schematically showing another endodonticmethod in which the high-velocity jet is directed toward the dentinthrough an inlet opening in a side of the tooth and a relief opening inthe top of the tooth is provided to reduce pressure buildup, if present,and to permit debridement.

FIG. 6C is a cross-section view schematically illustrating an embodimentof a positioning member prior to adherence to a tooth.

FIG. 6D is a cross-section view schematically illustrating an embodimentof a positioning member adhered to a side of a tooth and used to assistcoupling the distal end of the handpiece to the side of the tooth sothat the high-velocity jet may be directed through the inlet opening.

FIG. 7 schematically illustrates production of an acoustic wave causedby impingement of a high-velocity liquid jet onto a dentinal surface.

FIG. 8A is a cross-section view schematically illustrating cavitationbubbles formed near odontoblasts at the dentinal surface.

FIG. 8B schematically illustrates collapse of a cavitation bubble andformation of a cavitation jet near a dentinal surface.

FIGS. 9A-9C are scanning electron microscope photographs of dentinalsurfaces following treatment of the tooth with the high-velocity jet;FIG. 9A shows dentinal tubules in an apical area of a mature toothmagnified 1000×; FIGS. 9B and 9C show dentin and dentinal tubulesmagnified 1000× in an inclusion area of a juvenile tooth (FIG. 9B) andin a medial area of a mature root (FIG. 9C). A bar at the top left ofeach photo indicates the linear scale (in microns) for each photograph.

FIGS. 10A-10H schematically illustrate embodiments of a cap that may beattached to a distal end of a handpiece and fitted onto a tooth. FIGS.10A and 10C-10H are side views, and FIG. 10B is a partially explodedcross-section view.

FIG. 11 schematically illustrates a method for generating an acousticwave using a piezoelectric transducer.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present disclosure provides various apparatus and methods for dentaltreatments that overcome possible disadvantages associated withconventional root canal treatments. In certain embodiments, endodontictreatment methods (e.g., root canal therapy) comprise directing ahigh-velocity liquid jet toward a tooth. Impact of the jet causesacoustic energy to propagate from a site of impact through the entiretooth, including the root canal system of the tooth. The acoustic energyis effective at detaching substantially all organic material in the rootcanal system from surrounding dentinal walls. In many embodiments, thedetached organic material can be flushed from the root canal usinglow-velocity irrigation fluid. As used herein organic material (ororganic matter) includes organic substances typically found in healthyor diseased root canal systems such as, for example, soft tissue, pulp,blood vessels, nerves, connective tissue, cellular matter, pus, andmicroorganisms, whether living, inflamed, infected, diseased, necrotic,or decomposed.

FIG. 1 is a cross section schematically illustrating a typical humantooth 10, which comprises a crown 12 extending above the gum tissue 14and at least one root 16 set into a socket (alveolus) within the jawbone 18. Although the tooth 10 schematically depicted in FIG. 1 is amolar, the apparatus and methods described herein may be used on anytype of tooth such as an incisor, a canine, a bicuspid, or a molar. Thehard tissue of the tooth 10 includes dentin 20 which provides theprimary structure of the tooth 10, a very hard enamel layer 22 whichcovers the crown 12 to a cementoenamel junction 15 near the gum 14, andcementum 24 which covers the dentin 20 of the tooth 10 below thecementoenamel junction 15.

A pulp cavity 26 is defined within the dentin 20. The pulp cavity 26comprises a pulp chamber 28 in the crown 11 and a root canal space 30extending toward an apex 32 of each root 16. The pulp cavity 26 containsdental pulp, which is a soft, vascular tissue comprising nerves, bloodvessels, connective tissue, odontoblasts, and other tissue and cellularcomponents. The pulp provides innervation and sustenance to the tooththrough the epithelial lining of the pulp chamber 26 and the root canalspace 30. Blood vessels and nerves enter/exit the root canal space 30through a tiny opening, the apical foramen 32, near a tip of the apex 32of the root 16.

FIG. 2 depicts a pulpal surface of the dentin 20. The dentin 20comprises numerous, closely-packed, microscopic channels called dentinaltubules 34 that radiate outwards from the interior walls of the canalspace 30 through the dentin 20 toward the exterior cementum 24 or enamel22. The tubules 34 run substantially parallel to each other and havediameters in a range from about 1.0 to 3.0 microns. The density of thetubules 34 is about 5,000-10,000 per mm² near the apex 32 and increasesto about 15,000 per mm² near the crown.

The dentin 20 is continuously formed by specialized cells calledodontoblasts that secrete a mineralized substance that hardens intodentin. Odontoblasts form a single layer of cells between the dentin 20and the pulp. An odontoblast has a cell body that is located on thepulpal surface of the dentin 20 on a tubule 34 and a cytoplasmicportion, called the odontoblastic process, that extends into andsubstantially fills the associated tubule 34. The odontoblasts areconnected to each other with interodontoblastic collagen, and collagenfibrils may attach the odontoblast layer to the pulp. As a person ages,the odontoblasts continue to form dentin, which causes the root canalspace 30 to decrease in diameter.

FIG. 3 is a block diagram that schematically illustrates a compressorsystem 38 adapted to generate a high-velocity jet of fluid for use indental procedures. The compressor system 38 comprises a source ofcompressed gas 40 such as a pressurized air or gas source commonlyavailable in dental service installations. The compressed gas 40 may bepressurized in a range from about 50 pounds per square inch (psi) to 150psi including, for example, 100 psi. The compressed gas 40 may compriseany suitable commercially available gas including, for example, air,nitrogen, carbon dioxide, or a combination thereof. The compressed gas40 is pneumatically connected to a pump 46 via a regulator 42. Theregulator 42 can be used to regulate the pressure of the input gas to adesired pressure such as, for example, 40 psi. In some embodiments, thepump 46 comprises an air-driven hydraulic pressure intensifier that usesthe compressed gas 40 to increase the pressure of liquid received from afluid source 44. For example, a pressure intensifier having a 330:1pressure intensification ratio can increase the pressure of the liquidto about 13,200 psi using pressurized gas at 40 psi from the regulator42. Different pressure intensification ratios may be used in differentembodiments. By adjusting the gas pressure with the regulator 42, thepressure of the liquid output from the pump 46 can be selectablyadjusted to a desired value or range of values. In some embodiments, thepressure of the liquid can be adjusted within a range from about 500 psito about 50,000 psi. In certain embodiment, it has been found that apressure range from about 2,000 psi to about 11,000 psi produces jetsthat are particularly effective for endodontic treatments.

The fluid source 44 may comprise a fluid container (e.g., an intravenousbag) holding sterile water, a medical-grade saline solution, anantiseptic or antibiotic solution, a solution with chemicals ormedications, or any combination thereof. More than one fluid source maybe used. In certain embodiments, it is advantageous for jet formation ifthe liquid provided by the fluid source 44 is substantially free ofdissolved gases (e.g., less than 0.1% by volume) and particulates, whichcan act as nucleation sites for bubbles. In some embodiments, the fluidsource 44 comprises degassed distilled water. A bubble detector (notshown) may be disposed between the fluid source 44 and the pump 46 todetect bubbles in the liquid and/or to determine whether liquid flowfrom the fluid source 44 has been interrupted or the container hasemptied. The liquid in the fluid source 44 may be at room temperature ormay be heated and/or cooled to a different temperature. For example, insome embodiments, the liquid in the fluid source 44 is chilled to reducethe temperature of the high velocity jet generated by the compressorsystem 38.

In the embodiment depicted in FIG. 3, the high-pressure liquid from thepump 46 is fed to a regulator 48 and then to a handpiece 50, forexample, by a length of high-pressure tubing 49. The regulator 48 may beoperable with compressed gas from the source 40 and may be used toregulate the pressure of the liquid to a desired value. For example, inone embodiment, the regulator 48 reduces the 13,200 psi pressure fromthe pump 46 to about 12,000 psi. The regulator 48 may include waterpressure sensors and bleed-off valves (e.g., an air-driven needle valve)to provide the desired pressure and to permit an operator toactuate/deactuate water jet output from the handpiece 50.

The handpiece 50 receives the high pressure liquid and is adapted at adistal end to generate a high-velocity, coherent, collimated beam or jet60 of liquid for use in dental procedures. The handpiece 50 may be sizedand shaped to be maneuverable so that the jet 60 may be directed towardor away from various portions of the tooth 10.

The compressor system 38 may include a controller 51 that controls theoperation of the components of the system 38. The controller 51 maycomprise a microprocessor, a special or general purpose computer, afloating point gate array, and/or a programmable logic device. In oneembodiment, the controller 51 is used to operate the regulators 42, 48and the pump 46 so that the high-pressure liquid delivered to thehandpiece 50 is at a suitable working pressure. The controller 51 mayalso be used to control safety of the system 38, for example, bylimiting system pressures to be below safety thresholds and/or bylimiting the time that the jet 60 is permitted to flow from thehandpiece 50. In certain embodiments, the controller 51 may be used tovary or cycle the pressure of the liquid delivered to the handpiece 50,for example, by cycling pressures provided by one or both of theregulators 42, 48. In certain such embodiments, sinusoidal or sawtoothpressure variability may be used to provide corresponding variability inthe speed of the jet 60. In certain embodiments, cycle time for thepressure variability may be in a range from about 0.1 seconds to about 5seconds. Additionally and optionally, the controller 51 may regulate apulse intensifier device (not shown), such as a piezoelectrictransducer, that causes pulsations in the jet 60. For example, incertain embodiments, the jet 60 comprises a pulsed jet, which mayinclude a series of discrete liquid pulses, a continuous stream of fluidhaving spatially varying pressure, velocity, and/or area, or acombination thereof. The controller 51 advantageously may control theamplitude and frequency of the pulsations in the jet 60. In certainembodiments, the amplitude of the pressure variation may be in a rangefrom several hundred to several thousand psi. The pulse frequency may bein a range from about 0.1 Hz to about 10 MHz. For example, in someembodiments, a pulse frequency of about 1 MHz is applied to produce ajet comprising a series of droplets.

The system 38 may also include a user interface 53 that outputs relevantsystem data and accepts user input. In some embodiments, the userinterface 53 comprises a touch screen graphics display. In someembodiments, the user interface 53 may display information including theworking liquid pressure in the handpiece 50 and instructions and/orprocedures for operating on different tooth types (e.g., incisors,bicuspids, or molars). The user interface 53 may accept user input suchas a time setting that sets a maximum time during which the compressorsystem 38 will deliver the jet 60 and other useful endodontic treatmentoptions. For example, some embodiments permit an operator to select a“ramp up” and/or “ramp down” option in which the working liquid pressurecan be gradually increased or decreased, respectively. The ramp upoption advantageously may be used for initial aiming of the jet 60towards a suitable portion of the tooth 10, while the ramp downadvantageously may be used if the jet 60 is moved toward a sensitiveportion of the tooth 10 (e.g., the apex 32). The compressor system 38may also include a storage medium (e.g., volatile or nonvolatile memory)configured to store system operating information and executableinstructions, user preferences, preferred operating pressures and times,patient data, etc. In some embodiments, the storage medium compriseson-board memory of the controller 51 and/or additional random access orread-only memory, flash memory, removable memory cards, etc.

The compressor system 38 may include additional and/or differentcomponents and may be configured differently than shown in FIG. 3. Forexample, the system 38 may include an aspiration pump that is coupled tothe handpiece 50 (or an aspiration cannula) to permit aspiration oforganic matter from the mouth or tooth 10. In other embodiments, thecompressor system 38 may comprise other pneumatic and/or hydraulicsystems adapted to generate the high-velocity beam or jet 60. Forexample, certain embodiments may utilize apparatus and systems describedin U.S. Pat. No. 6,224,378, issued May 1, 2001, entitled “METHOD ANDAPPARATUS FOR DENTAL TREATMENT USING HIGH PRESSURE LIQUID JET,” and/orU.S. Pat. No. 6,497,572, issued Dec. 24, 2002, entitled “APPARATUS FORDENTAL TREATMENT USING HIGH PRESSURE LIQUID JET,” the entire disclosureof each of which is hereby incorporated by reference herein.

Moreover, in other embodiments, the high-velocity jet 60 may begenerated by systems other than the high-pressure compressor system 38,such as, for example, by a pump system. In one such embodiment, anelectric motor drives a pump that is in fluid communication with aliquid reservoir. The pump increases the velocity of the liquid so as toprovide a narrow beam of high-velocity liquid from the handpiece 50. Insome embodiments, multiple pumps are used. As is well known fromBernoulli's law, the total pressure in a flowing fluid includes static(e.g., thermodynamic) pressure plus dynamic pressure (associated withfluid kinetic energy). A skilled artisan will recognize that staticpressures in motor-driven pump systems may be less than static pressuresin compressor systems, because the motor-driven pump primarily increasesthe dynamic pressure (e.g., the fluid velocity) of the liquid. The totalpressures (static plus dynamic) achieved are comparable in manyembodiments of compressor systems and pump systems.

FIGS. 4 and 4A are cross-section views that schematically illustrate oneembodiment of the handpiece 50 adapted for forming the high-velocity jet60. The handpiece 60 comprises an elongated tubular barrel 52 having acentral passageway 54 extending axially therethrough. The handpiece 50has a proximal end 56 that is adapted to engage tubing from theregulator 48 in order for the passageway 54 to be in fluid communicationwith the high pressure liquid delivered by the compressor system 38. Thebarrel 52 may include features 55 that enhance grasping the handpiecewith the fingers and thumb of the operator. A distal end 58 of thebarrel 52 (shown in closeup in FIG. 4A) includes a threaded recessadapted to engage complementary threads of an orifice mount 62, which isconfigured to hold an orifice jewel 64 at an end thereof. The orificemount 62 is tightly screwed into the distal end 58 of the barrel 52 tosecure the orifice jewel 64 adjacent to a distal end of the passageway52.

The orifice jewel 64 may comprise a circular, disc-like element having asmall, substantially central orifice 66 formed therein. The orificejewel 64 may be fabricated from a suitably rigid material that resistsdeformation under high pressure such as, for example, synthetic sapphireor ruby. The orifice mount 62 advantageously secures the orifice jewel64 substantially perpendicular to the passageway 54 so that highpressure liquid in the passageway 54 can flow through the orifice 66 andemerge as a highly collimated beam of fluid traveling along alongitudinal jet axis 70 that is substantially coaxial with the barrel52 of the handpiece 50. In some embodiments, the distal end 58 of thehandpiece 50 may include additional components, for example, to assistguiding or directing the jet 60 and/or to provide aspiration. Also, asfurther described below, the distal end 58 of the handpiece 50 may beadapted to receive various end caps that assist guiding the jet 60toward the pulp cavity 26.

FIG. 5A is a cross-section schematically illustrating the distal end 58of an embodiment of the handpiece 50 to further illustrate formation ofthe jet 60. The orifice jewel 64 is secured at the distal end of thehandpiece 50 and forms a tight seal to prevent leakage of high-pressureliquid 68 contained in the passageway 54. In the depicted embodiment,the orifice jewel 64 has a proximal side that is substantially flat anda distal side that is concave (e.g., thinnest near the orifice 66). Theorifice 66 has a substantially circular cross-section with a diameter“D.” The axial length of sides 69 of the orifice 66 is “L.” The diameterD may be in a range from about 5 microns to about 1000 microns. Otherdiameter ranges are possible. In various embodiments, the diameter D maybe in a range from about 10 microns to about 100 microns, a range fromabout 100 microns to about 500 microns, or range from about 500 micronsto about 1000 microns. In various preferred embodiments, the orificediameter D may be in a range of about 40-80 microns, a range of about45-70 microns, or a range of about 45-65 microns. In one embodiment, theorifice diameter D is about 60 microns. The ratio of axial length L todiameter D may be about 50:1, 20:1, 10:1, 5:1, 1:1, or less. In oneembodiment, the axial length L is about 500 microns. In certainembodiments, the ratio of axial length L to diameter D is selected sothat transverse width of any boundary layers that may form on the sides69 of the orifice 66 have a transverse width that is sufficiently small,for example, much less than the diameter D. In preferred embodiments,the orifice diameter is 40-80 microns, and more preferably 45-70microns, and even more preferably 45-65 microns. The axial length of theorifice is preferably no greater than ten times the diameter of theorifice, and the liquid pressure at the input side of the orifice is7,000 to 15,000 psi. In one embodiment, the orifice is about 60 micronsin diameter, the axial length of the orifice about 500 microns, and theliquid pressure at the input side of the orifice about 11,000 psi. Sincethe output side of the orifice is at atmospheric pressure, the pressuredrop at the orifice will be only slightly less than the pressure at theinput side of the orifice. This combination of parameters provides ahigh velocity, high momentum, collimated, coherent liquid beam that isefficacious for cleaning without significant dentinal erosion.

In certain embodiments, the sides 69 of the orifice 66 are machined,polished, or otherwise processed to be substantially smooth in order toreduce or prevent formation of turbulence, cavitation, bubbles, fluidinstabilities, or other effects that may interfere with substantiallysmooth, laminar flow of the liquid through the orifice 66. For example,in certain such embodiments, the sides 69 have a root-mean-square (rms)surface roughness less than about 10 microns, less than about 1 micron,or less than about 0.1 microns. In other embodiments, the rms surfaceroughness is much smaller than the diameter D of the orifice such as,for example, less than about 0.1 D, less than about 0.01 D, less thanabout 0.001 D, or less than about 0.0001 D. Additionally, highlydemineralized liquids may be used to reduce buildup of impurities alongthe sides 69, which advantageously may increase the useful operatinglifetime of the orifice jewel 64.

As schematically depicted in FIG. 5A, the high pressure liquid 68 in thepassageway 54 emerges through the orifice 66 as a high-velocity,collimated jet 60 traveling substantially along the jet axis 70 with avelocity, v. In some embodiments of the compressor system 38, the jetvelocity is estimated to be proportional to (P/ρ)^(1/2), where P is theliquid pressure in the passageway 54 and p is the density of the liquid.In certain embodiments, water pressurized to about 10,700 psi emergesfrom the orifice as a jet 60 having a velocity of about 220 m/s. Byadjusting the liquid pressure delivered by the compressor system 38, thehandpiece 50 can deliver jets having different velocities. In someembodiments, the user interface 53 permits the operator to selectivelyadjust system pressures so that the velocity of the jet is suitable fora particular dental treatment.

In certain embodiments of the system 38, the liquid used to form the jet60 is substantially free from dissolved gases (e.g., less than about0.1% per volume). If the dissolved gas content of the liquid is toohigh, bubbles may formed at the nozzle orifice 66 due to the pressuredrop. Additionally, the pressure drop should preferably be sufficientlylow to prevent formation of vapor at the distal end of the orifice 66.The presence of substantial vapor, gas or bubbles, or particlecontaminants in the liquid may cause a significant portion of the energyof the liquid jet 60 to be depleted, and there may be insufficientkinetic energy (and/or momentum) to provide efficient cleaning of theroot canal system. When used for removing tissue and/or organic matterfrom root canals, the effectiveness of the device disclosed in U.S. Pat.No. 6,497,572, issued Dec. 24, 2002, and entitled “Apparatus for DentalTreatment Using High-Pressure Liquid Jet,” is significantly increased byusing liquids that are free (or at least substantially free) ofdissolved gases (as well as bubbles) to form the high-velocity jet.Preferably, the liquid is bubble-free distilled water, and theconcentration of dissolved gases is no more than e.g. 0.1% by volume. Inuse, the liquid beam is preferably directed at the floor of the pulpchamber at an oblique angle relative to the long axis of the rootcanals. Although the chamber fills with liquid, the beam has sufficientvelocity to impact the submerged dentin with great force. Uponimpingement, the primary, collimated coherent beam from the jetapparatus generates a high-energy acoustic pressure wave that propagatesalong the body of the tooth. At the dentinal surfaces of the main andside canals, the acoustic wave causes any surrounding liquid tocavitate. This cavitation is a surface effect cavitation caused byconversion of the water (or other liquid) from a liquid state to a vaporstate. Due to the high energy required for such conversion, collapse ofthe cavitation bubble occurs with great force against the surface of thedentin and cleans through creation of cavitation-induced sub-jets whichradiate inward toward the surface from the point of collapse of thecavitating vapor. The substantially gas-free liquid is preferred for theabove described cavitation process. If the dissolved gas content of theliquid is too high, bubbles will be formed at the nozzle orifice due tothe pressure drop. Additionally, the pressure drop should preferably besufficiently low to prevent formation of vapor at the nozzle orifice.The presence of significant vapor, gas or bubbles causes much of theenergy of the beam to be depleted, and there will be insufficient energyto generate the liquid to vapor-phase cavitation, which is a surfaceeffect.

The jet 60 emerges from the distal end of the orifice 66 as a beam offluid traveling substantially parallel to the jet axis 70. Such jets arecalled “collimated” jets. In certain embodiments, the angular divergenceof the jet 60 is less than about 1 degree, less than about 0.1 degree,or less than about 0.01 degree. In other embodiments, jet beams withdifferent angular divergences may be used. In some embodiments, the jet60 can travel as a collimated beam for a distance of about 1 to 3 inchesbefore the jet 60 begins to disperse (e.g., due to entrainment of air).In certain embodiments, the jet 60 may travel a distance at leastseveral thousand times the jet diameter D before beginning to disperse.

As described above, it may be advantageous for the sides 69 of theorifice 66 to be sufficiently smooth that liquid flows through theorifice 66 in a substantially laminar manner. In certain embodiments,the transverse width of any boundary layers formed along the sides 69 ofthe orifice 66 is much smaller than the diameter D, and, away from theboundary layers, the speed of the jet 60 is substantially constantacross the width of the orifice. FIG. 5B is a graph schematicallyillustrating an example velocity profile of the jet 60 after it hasemerged from the distal end of the orifice 66. The graph depicts flowvelocity in the direction of the jet axis 70 versus a distancetransverse (e.g., orthogonal) to the jet axis 70. In this exampleembodiment, away from narrow boundary layers near the outer surface ofthe jet 60 (e.g., near 0 and D on the graph), the jet velocity issubstantially constant across the width of the jet. Jets havingsubstantially constant velocity profiles are called “coherent” jets. Inother embodiments, the velocity profile of the jet 60 is notsubstantially constant across the width of the jet 60. For example, thejet velocity profile in certain embodiments is a parabolic profilewell-known from pipe flow.

In certain embodiments, the compressor system 38 is configured todeliver a coherent, collimated jet 60 of high-velocity liquid. Acoherent, collimated jet will be denoted herein as a “CC jet.” Thefollowing example provides various representative properties of a CC jet60 that can be generated using an embodiment of the system 38. In thisexample system, the diameter D and the axial length L of the orifice 66are 60 microns and 500 microns, respectively. In one embodiment, thepressure of the liquid (degassed, distilled water) in the handpiece 50is about 8,000 psi, which produces a jet velocity of about 190 m/s. Themass discharge rate of the jet is about 0.5 g/s, and the jet can producea force of about 0.1 Newton when impacting a surface at normalincidence. The jet provides a kinetic power of about 10 Watts. If thejet is directed toward a tooth for about 10 seconds, the jet can delivera momentum (or impulse) of about 1 kg m/s and an energy of about 100Joules (about 23 calories).

In other embodiments, the CC jet is produced from liquid pressurized toabout 2500 psi. The jet velocity is about 110 m/s, and volume flow rateis about 0.3 mL/s. The CC jet can produce about 2 W of kinetic power.The jet 60 may remain substantially collimated over propagation lengthsfrom about 1 cm to about 30 cm in various embodiments.

The energy flux produced by the liquid jet is the kinetic power of thejet divided by the transverse area of the jet beam. The energy flux maybe in a range from about 1 kW/cm² to about 1000 kW/cm². In someembodiments, the energy flux is in a range from about 50 kW/cm² to about750 kW/cm², including, for example, 70 kW/cm², 175 kW/cm², 350 kW/cm²,and 550 kW/cm². In one experiment, a CC jet was directed toward adentinal surface of a tooth, and widespread acoustic noise (possibly dueto acoustic cavitation) was detected in the tooth when the energy fluxof the jet exceeded about 75 kW/cm². At the onset of detectable acousticnoise, the CC jet had the following properties: velocity of about 110m/s, kinetic power of about 2 W, and mass flow rate of about 0.3 g/s.The pressure producing the CC jet was about 2500 psi.

By using different fluid working pressures and/or orifice diameters,jets having different properties can be generated. For example, incertain embodiments, the mass discharge rate may be in a range fromabout 0.01 g/s to about 1 g/s, the jet velocity may be in range fromabout 50 m/s to about 300 m/s, the jet force may be in a range fromabout 0.01 N to about 1 N, and the jet power may be in a range fromabout 0.1 W to about 50 W. In various endodontic treatments, the jet isapplied to a tooth for a time in a range from about 1 second to 120seconds. Accordingly, in such treatments, the jet can deliver momentum(or impulse) in a range of about 0.01 kg m/s to about 100 kg m/s, andenergy in a range of about 0.1 J to about 500 J. In some embodiments, anenergy range from about 20 J to about 400 J may be effective atproviding cleaning of the root canal system without causing substantialerosion of dentin. A person of ordinary skill will recognize that thecompressor system 38 can be configured to provide liquid jets having awide range of properties that may be different from the example valuesand ranges provided herein, which are intended to be illustrative andnon-limiting.

In various dental treatments, the compressor system 38 delivers a jet60, which advantageously may be a CC jet, that is directed toward one ormore portions of a tooth in order to, for example, excise and/oremulsify organic material, provide irrigation, and/or generate acousticenergy for delaminating organic matter from the pulp cavity 26.

FIG. 6A schematically illustrates one embodiment of an endodontictreatment for diseased pulp in the tooth 10. A drill or grinding tool isinitially used to make an opening 80 in the tooth 10. The opening 80 mayextend through the enamel 22 and the dentin 20 to expose and provideaccess to pulp in the pulp cavity 26. The opening 80 may be made in atop portion of the crown 12 of the tooth 10 (as shown in FIG. 3) or inanother portion such as a side of the crown 12 or in the root 16 belowthe gum 14. The opening 80 may be sized and shaped as needed to providesuitable access to the diseased pulp and/or some or all of the canalspaces 30. In some treatment methods, additional openings may be formedin the tooth 10 to provide further access to the pulp and/or to providedental irrigation.

The handpiece 50 may be used to deliver a jet 60 of liquid to a portionof the tooth 10. The jet 60 advantageously may, but need not, be a CCjet. The jet 60 can be used to cut through organic material in the pulpchamber 28. Additionally, as will be further described below, the jet 60may be directed toward hard surfaces of the tooth 10 (e.g., the dentin20) to generate acoustic energy, which may propagate through the dentin20, the dentinal tubule, and the organic material in the root canalspace 30. The acoustic energy causes detachment of organic material fromthe dentin 20 without requiring that the jet directly impact the organicmaterial. In certain embodiments, the acoustic energy has been found tobe effective in causing detachment of the entire body of pulp (and otherorganic material) from within the pulp chamber 28 and/or root canalspace 30, without the use of endodontic files. The jet 60 preferablyshould have insufficient energy, energy flux, and/or momentum to damageor substantially erode the dentin 20.

In some treatment methods, the operator can maneuver the handpiece 50 todirect the jet 60 around the pulp chamber 28 during the treatmentprocess. The distal end of the handpiece 50 may be held about 1 inchfrom the tooth 10 so that the liquid impacts a portion of the tooth 10as a substantially collimated coherent beam. The jet 60 may providesufficient force to cut through and/or emulsify some or all of theorganic material in the pulp chamber 28. The flow of liquid from the jet60 may create sufficient swirling or turbulent flow to remove the cutand/or emulsified organic material from the pulp cavity 26 so that itcan be aspirated from the mouth of the patient. In other treatmentembodiments, pulpal tissue in the pulp chamber 28 may be removed viaconventional techniques prior to (and/or during) liquid jet treatment toexpose a portion of the dentin 20. The jet 60 may then be directed tothe exposed portion.

The jet 60 may be directed toward the floor 82 of the pulp chamber 28(see, e.g., FIG. 7). In some methods, the jet 60 is directed toward thefloor 82 (and/or walls) of the pulp chamber 28 advantageously at asubstantial angle (e.g., 15-50 degrees) relative to the long axis of theroot canal space 30 to ensure that the jet does not directly impact theapical portion of the canal space 30, thereby reducing a possibilitythat the force (and/or pressure) imparted by the jet 60 will causedamage to healthy tissue around the apical foramen 34. Accordingly,certain disclosed treatment methods advantageously may be used on “openapex” teeth having underdeveloped and/or enlarged apices, becauseimpingement of the jet 60 in the pulp chamber 28 will not harm theperiapical portion of the tooth 10. Additionally or optionally, the jet60 can be directed toward one or more sides of the pulp chamber 28 so asto impact the dentin 20. In some embodiments, the jet is directed toseveral locations in or on the tooth 10. An advantage of some methods isthat the impact of the jet 60 on the dentin 20 does not causesignificant erosion or destruction of the dentin 20 within the tooth 10.Accordingly, such methods may be minimally invasive in comparison withconventional root canal procedures.

The pulp cavity 26 may fill with fluid during the treatment. Forsufficiently high working pressures, the jet 60 will have sufficientvelocity to impact submerged dentin 20 with enough force to provideeffective treatment. In certain embodiments of the treatment method, oneor more properties of the jet 60 are temporally varied during thetreatment. For example, the working pressure may be varied to ramp up orramp down the jet velocity or to cause the jet to alternate betweenhigh-speed flow and low-speed flow. The jet 60 may comprise a pulsed jetwith pulsation amplitude and/or frequency selected to provide effectivetreatment. A combination of the above treatment methods may be used,serially or in alternation.

As noted above, detachment of the organic material within the root canalsystem from the surrounding dentin 20 does not require that the jet 60impact the organic material in the root canal space 30. Rather, the jet60 may be directed against a dentinal wall (e.g., in the pulp chamber28), which couples acoustic energy to the tooth 10 so as to causedetachment of the organic material. In some methods, the detachmentoccurs relatively quickly after the jet 60 impinges on the dentinal wall(e.g., within a few seconds) and may occur substantially simultaneouslythroughout one or more root canal spaces 30 of the tooth 10.

In one presently preferred method schematically illustrated in FIG. 6B,the jet beam 60 is introduced into an inlet opening 84 formed in theside (e.g., buccal or lingual surface) of the tooth 10 with aconventional dental drill. The opening 84 may be formed near thecementoenamel junction 15. In some procedures, a portion of the gum 14is depressed to provide access to the intended position of the opening84 near the cementoenamel junction 15. The opening 84 may have adiameter in a range from about 1 mm to about 2 mm and may extend fromthe exterior surface of the tooth 10 to the pulp chamber 28. In someembodiments, the diameter is about 1.2 mm. Different diameters may beused in other embodiments. The opening 84 is thus generally transverseto the long axis of any root canal space 30 and ensures that the energyof the jet 60 will not be directed down any canal spaces 30. A benefitof providing the opening 84 in the side of the tooth 10 is that lesshard tissue of the tooth 10 is damaged than if the opening were formedthrough the occlusal surface of the tooth 10. Although it is presentlypreferred to use a single inlet opening 84 to reduce invasiveness of theprocedure, in other methods, two or more inlet openings may be used.

FIGS. 6C and 6D are cross-section views schematically illustrating anembodiment of a positioning member 130 that may be used to assistcoupling and orienting the distal end 58 of the handpiece 50 to thetooth 10 so that the high-velocity jet 60 is directed through the inletopening 84 in the side of the tooth 10. In the illustrated embodiment,the positioning member 130 comprises a collar portion 134 that may begenerally disk-like in shape. The collar portion 134 may have a width ina range from about 1 mm to about 10 mm. The collar portion 134 may havea substantially central opening 136 having a diameter approximatelyequal to the diameter of the inlet opening 84. In some embodiments, thecollar portion 134 is formed from a flexible material (such as anelastomer) so that it can conform to the surface of the tooth 10. Anadhesive (such as a light-cured orthodontic adhesive) may be included ona surface 134 a of the collar portion 134 to enable the positioningmember 130 to adhere to the tooth 10. In some embodiments, a detachable,elongated peg 138 may be used to position the position member 130 sothat the central opening 136 in the collar portion 134 is aligned withthe inlet opening 84 in the tooth 10. A distal end of the peg 138 may besized to fit within the opening 84. When the positioning member 130 isin position on the tooth 10 and the adhesive has sufficiently cured, thepeg 138 may be removed, leaving the positioning member 130 adhered tothe side of the tooth 10 (see FIG. 6D). Additionally or alternatively,the collar portion 134 may include alignment guides disposed near theopening 136 to assist positioning the member 130 over the opening 84.For example, a circular ridge, having an outside diameter slightlysmaller than the inside diameter of the opening 84, may be formed on thesurface 134 a around the opening 136 and used to align the openings 84and 136.

The positioning member 130 may include mounting portions 132 aconfigured to engage complementary mounting portions 132 b disposed onthe distal end 58 of the handpiece 50. For example, the mountingportions 132 a, 132 b may comprise a standard, quick-turn connector suchas a Luer-lock. FIG. 6D schematically illustrates the handpiece 50before (or after) engagement with the positioning member 130. Whenengaged with the positioning member 130, the handpiece 50 advantageouslyis oriented so that the jet axis 70 is substantially longitudinallyaligned with the inlet opening 84. Moreover, the positioning member 130may stabilize the handpiece 50 against unwanted movement. Accordingly,upon actuation, the jet 60 will be directed through the opening 84 andinto the pulp cavity 26. As further described below with reference toFIG. 10B, the distal end 58 of the handpiece 50 may comprise one or morepressure sensors adapted to sense when the distal end 58 is securelyengaged with the positioning member 130. In such embodiments, the systemmay not permit the jet 60 to be actuated until a sufficiently secure fitand proper alignment are indicated by signals from the pressure sensors.

When the distal end 58 of the handpiece 50 is engaged with thepositioning member 130, the jet 60 may be directed through the inletopening 84 so that it impacts the dentinal wall and causes detachment ofthe organic material in the root canal spaces 30. After the treatment iscompleted, the positioning member 130 may be removed from the tooth 10using any well-known technique for releasing the adhesive. Remainingadhesive, if present, may function as bonding for restorative materialused to close the defect.

To reduce possible buildup of fluid pressure within the pulp cavity 26,a relief opening 88 may be formed in the top side (e.g., occlusalsurface) of the tooth 10. The relief opening 88 may be formed on abuccal or lingual surface. The diameter of the relief outlet or opening88 may be larger than that of the inlet opening 84, for example, about 2mm to about 3 mm. In some methods, the diameter of the relief opening 88may be about the same as (or smaller than) the diameter of the inletopening 84 (e.g., about 1.2 mm in one embodiment). The relief opening 88also serves to facilitate debridement and evacuation of the detachedorganic material. The diameter of the relief opening 88 advantageouslymay be large enough to permit flushing out pulp fragments. In somemethods, two or more relief openings 88 may be used.

Those skilled in dentistry will recognize that the inlet and reliefopenings 84, 88 are quite small relative to the openings required forconventional root canal procedures, thus preserving valuable toothstructure. For example, in some methods, even though two openings 84, 88are used, less tooth material is removed than in a conventional rootcanal procedure using a single, standard-sized occlusal opening.Moreover, many patients have existing coronal defects (e.g., decay,restorations, preparations, etc.), and it may be possible to form one orboth of the openings simply by removing material other than healthytooth tissue, such as a filling. Fillings on one or more sides of thetooth 10 may also be used to form the openings 84, 88. In any event,once the jet has caused acoustically induced detachment of the organicmaterial, low pressure flushing fluid (such as water) may be introducedinto either or both the openings 84, 88 to irrigate the canal space 30and flush out the organic material. Additionally and optionally, manualextraction of organic material may be performed with a dentalinstrument.

Certain teeth, particularly molars and/or wisdom teeth, may be difficultto access in conventional root canal therapies due to limited workingspace in the back of the mouth. Due to the difficulties or inconvenienceof coronal access to these teeth in conventional root canal therapies,some of these teeth, which would otherwise be treatable, may instead beextracted. An advantage of some embodiments of the disclosed methods isthat by permitting a wider range of access with the liquid jet 60 (e.g.,on or through coronal, lingual, and/or buccal surfaces), theacoustic-induced detachment of organic material can save the tooth andreduce the likelihood of its extraction.

Without subscribing to any particular theory of operation, FIG. 7schematically illustrates an explanation for the effectiveness of thetreatment methods described herein. FIG. 7 depicts the jet 60 impactingthe dentin 20 of the tooth 10. Upon impact, a portion of the energyand/or momentum carried by the jet 60 generates an acoustic pressurewave 100 that propagates through the body of the tooth 10. In additionto propagating through the dentin 20, the acoustic wave 100 maypropagate through organic material in the root canal space 30 and in thetubules of the dentin 20. The acoustic wave 100 may include acousticenergy with acoustic frequencies in a range from about 1 Hz to above 5MHz such as, for example, up to about 10 MHz. The acoustic wave 100 mayhave frequency components in the ultrasonic frequency range, e.g., aboveabout 20 kHz. In some cases, the frequency range may include megasonicfrequencies above about 1 MHz. The acoustic wave 100 may include otherfrequencies as well.

At the dentinal surfaces of the root canal space 30 and tubules, theacoustic wave 100 may cause surrounding liquid to cavitate. Thiscavitation may be a surface effect cavitation caused by conversion ofthe water (or other liquid) from a liquid state to a vapor state. If theacoustic energy in the wave 100 is sufficiently large, the cavitationprocesses may include inertial cavitation wherein sufficiently lowpressures caused by the acoustic wave 100 induce formation and collapseof bubbles in liquid near the dentinal surfaces. For smaller acousticenergies, non-inertial (or gas) cavitation may play a more significantrole. In such cases, dissolved gases, tissue debris, and impurities actas nucleation centers for the formation of cavitation bubbles.Cavitation may also occur at pore sites across the microporous surfaceof the dentin 20. The cavitation bubbles oscillate in response to theacoustic wave 100, and amplitude of the oscillations may grow asadditional gas is absorbed by the bubble.

Due to the relatively high energy required for formation of cavitationbubbles, collapse of the cavitation bubble occurs with great forceagainst the surface of the dentin 20. Bubble collapse near a surface isknown to occur asymmetrically and may result in formation of cavitationjets that radiate toward the surface and produce locally very highpressures and/or elevated temperatures. In some cases, the acoustic wave100 may also generate fluid motions (acoustic streaming) that enhancedisruption of organic matter. Acoustic streaming also may be effectiveat transporting or flushing detached organic matter out of the rootcanal space 30 and/or the tubules.

Accordingly, in certain methods, the acoustic wave 100 cleans the rootcanal system through processes including formation and collapse ofcavitation bubbles, radiation of cavitation jets toward dentinalsurfaces, acoustic streaming, or a combination thereof. In the process,the organic material may be broken into small pieces or particles, whichcan be irrigated from the pulp cavity 26. In some treatment methods,these cavitation processes may produce transient, localized highpressure and/or elevated temperature zones that disrupt, detach, and/ordelaminate organic matter near root canal surfaces. For example,cavitation-induced effects may detach odontoblasts from the dentinalsurface and effectively remove a portion of the odontoblastic processfrom the tubule. Cavitation-induced effects may also disrupt and/ordetach the collagen fibrils that attach the odontoblast layer to thepulp in the interior of the canal space 30. Cavitation-induced effectsmay also occur in interior regions of the pulp cavity 26 (e.g., awayfrom the dentinal surfaces) and may disrupt and/or loosen organicmaterial in the interior regions, thereby making this material morereadily removable from the pulp cavity 26.

Cavitation effects are believed to be formed everywhere the acousticwave 100 propagates with sufficient energy. Accordingly, it isadvantageous for the jet 60 to have sufficient energy and/or momentum togenerate an acoustic wave 100 capable of causing cavitation effectsthroughout substantially the entire root canal system but withoutcausing harm to the tooth 10. For example, if the jet diameter D is toosmall and the momentum of the jet beam too high, impact of the beam maycause significant dentinal erosion. On the other hand, if the beamdiameter D is too large and the momentum of the jet beam too low, thebeam may have insufficient energy to produce an acoustic pressure wave100 capable of causing cavitation. For example, in certain methods, thejet energy incident on the tooth is greater than about 20 J to provideeffective cleaning but less than about 400 J to prevent dentinalerosion. In some methods, acoustic cavitation effects occursubstantially throughout the root canal system when certain jet 60properties are above threshold values. For example, in one experimentmentioned above, widespread acoustic noise (possibly caused by acousticcavitation) was detected in a tooth only when the energy flux of the jet60 was greater than about 75 kW/cm². At the onset of detectable acousticnoise, the jet had a power of about 2 W, a velocity of about 115 m/s, amass flow rate of about 0.3 g/s, and provided a force of about 0.03 N.The efficiency of conversion of jet kinetic energy into acoustic energywas estimated to be about 2%.

A portion of the acoustic wave 100 may also propagate through tissue andbone adjacent the tooth 10. However, the energy carried by this portionof the acoustic wave 100 may be relatively small due to the acousticimpedance mismatch between the dentin 20 and nearby tissues and bone.Accordingly, cavitation-induced effects may be substantially reduced intissues surrounding the tooth 10, and the endodontic methods describedherein will not significantly damage the surrounding tissues.

FIGS. 8A and 8B are cross-section views that schematically illustratesome of the cavitation processes that clean a surface 104 of the dentin20. As depicted in FIG. 8A, odontoblasts 106 are located near thesurface and the odontoblastic process extends into the tubules 108. Theacoustic wave 100 induces oscillation and collapse of cavitation bubbles110, which generates transient localized heat and/or pressure thatdisrupts and detaches the odontoblasts 106 from the dentinal surface104. Cavitation bubbles may also form and collapse within the tubules108, thereby causing disruption of the odontoblastic processes in thetubules 108. FIG. 8B schematically depicts collapse of an initiallyspherical cavitation bubble 110 (shown in (i)) located near the body oforganic matter 112 adjacent the dentinal surface 104 and filling thecanal. In (ii), the side of the bubble 110 away from the surface 104 isperturbed from its spherical shape. In (iii), fluid 114 from theinterior of the pulp cavity 26 penetrates the perturbed side of thebubble 110. In (iv) the fluid 114 has formed a cavitation jet 116radiating toward the surface 104. The energy and momentum of thecavitation jet 116 breaks up and disperses the organic matter 112.

FIGS. 9A-9C are scanning electron microscope photographs of the dentinalsurface showing the surprising effectiveness of the removal of organicmatter by the acoustic effect. FIG. 9A shows dentinal tubules in anapical area of a mature tooth magnified 1000×. FIGS. 9B and 9C showdentin and dentinal tubules magnified 1000× in an inclusion area of ajuvenile tooth (FIG. 9B) and in a medial area of a mature root (FIG.9C). A bar at the top left of each photo indicates the linear scale (inmicrons) for each photograph. As can be seen in FIGS. 9A-9C, thedentinal surfaces are almost entirely free from organic matter, whichappears to have been literally ripped away from the dentin. Flow ofliquid in the root canal space 30 flushes and irrigates the organicmatter from substantially all the root canal space 30 and the tubules.Returning to FIG. 2, this photograph shows an apical area of a maturetooth magnified 2000× and viewed at a slight slant from perpendicular toshow that the tubules have been cleaned down to a distance of about 3microns. FIGS. 2 and 9A-9C demonstrate that cleaning of the dentinalsurface is very effective and that almost no remnants of organicmaterial remain after treatment.

As mentioned previously, it has been found that the cleaning does notrequire that the liquid jet 60 be aimed down the root canal space 30,although that may be beneficial in certain isolated cases where thecanal space 30 is very narrow and/or filled with dry material.Additionally, it has been found in some embodiments that the pulp cavity26 need not be prepared or pre-treated (e.g., by removing root canalmatter with one or more endodontic files) before application of the jet.Impingement of the jet 60 onto the dentin 20 in the pulp chamber 28 issufficient in most cases to generate the acoustic wave 100 that causesthe cleaning. Accordingly, in most cases, it is the acoustic wave 100and not direct impact of the jet 60 that causes the cleaning,particularly for the dentinal surfaces near the apex of the root canalspace 30, which are remote from the pulp chamber 28. For example,examination of FIGS. 2 and 9A-9C shows that organic material has beenremoved from apical dentinal tubules, which are not possible to reachdirectly with the liquid jet beam. In certain embodiments, the jet beam60 is capable of delivering sufficient energy to the tooth 10 to removeat least 90 percent of the organic material from the root canal system.In other embodiments, at least 95 percent of the organic material isremoved. Preferably, the jet beam should be capable of removingsubstantially all the organic material from the root canal space 30 andfrom at least a portion of the tubules. The treatment time during whichthe high-velocity jet is directed toward the tooth 10 may range fromabout 1 second to about 120 seconds. In some embodiments, the treatmenttime is from about 10 seconds to about 30 seconds. In other embodiments,the treatment time is no more than 10 seconds such as, for example, lessthan about 5 seconds, less than about 2 seconds, less than about 1second, less than about 0.5 second, or less than about 0.1 second.

The high-velocity jet 60 may produce significant mechanical power (e.g.,tens of Watts in some embodiments). When the jet 60 is directed towardthe tooth 10, a fraction of this mechanical power may go toward heatingthe tooth 10 as well as nearby teeth and gums. To avoid discomfort tothe patient, in some embodiments, excess heat, if present, may beremoved by, for example, irrigating the tooth under treatment with astream of liquid (e.g., water at room temperature or cooler). The streamof liquid can absorb and carry away some or all of the excess heat, ifpresent, that may be produced by the jet 60. The stream of liquid may beaspirated from the patient's mouth.

The methods described herein may be used as standalone treatments forroot canal procedures, or they may be used in conjunction with otherdental treatments (which may or may not involve liquid jet methods).

The high-velocity jet treatment methods described herein may beparticularly effective in certain system operating ranges. For example,a jet having an energy flux greater than about 75 kW/cm² may beparticularly effective.

The apparatus and methods described above may include additional devicesand components configured to provide additional functionality to theendodontic treatment system. FIGS. 10A-10H schematically illustrateembodiments of a contact member configured as a cap 120 that may beattached to and detached from the distal end 58 of the handpiece 50. Insome embodiments, the cap 120 may have threads that engage complimentarythreads on the distal end 58 of the handpiece 50 (see, e.g., FIG. 10B).The cap 120 can be fitted around the crown 12 of the tooth 10 and usedto orient the jet 60 toward a suitable opening into the pulp chamber 26.The cap 120 may be used to orient the distal end 58 of the handpiece 50so that the liquid jet 60 is directed obliquely at a dentinal surface onthe floor 82 (and/or sides) of the pulp cavity 26 and not directly downany of the canal space 30. The cap 120 may be formed from a transparentor translucent material and may be sufficiently flexible to fit aroundteeth having a range of sizes. In some embodiments, the distal end 58 ofthe handpiece 50 may be rotatable and/or extendable with respect to thecap 120 so that the jet 60 may be moved closer to or further from adesired tooth portion. The cap 120 may include an outflow opening topermit organic material and liquid to be evacuated from the tooth 10.Alternatively, the cap may include a suction port so that fluid may beremoved from the pulp chamber at substantially the same volume as it isintroduced. The suction port thus prevents any of the removed diseasedtissue and liquid from entering the patient's mouth. Another aspect ofthe invention comprises introducing a volume of liquid in the form of ajet into a pulp chamber of a tooth and removing a volume of liquid fromthe pulp chamber at substantially the same rate that it is introduced.Preferably, removal is accomplished by suction. In certain embodiments,the distal end 58 of the handpiece 50 may include multiple orificeswhich provide multiple jets, and the cap 120 may be used to orient thehandpiece 50 such that jets are directed not only at the floor 82(and/or sides) of the pulp chamber 28, but also towards entrances to thecanal spaces 30. In some embodiments, the handpiece 50 may also betilted and rotated to allow the jet 60 to be aimed axially into allcanal openings.

As schematically shown in FIGS. 10C-10H, a plurality of caps 120 may beconfigured to fit over teeth of different sizes and shapes.Advantageously, each different cap 120 may be color coded to permit easyselection by the dentist during a treatment procedure. The cap 120 mayalso be sized and shaped to fit within an opening formed in the tooth 10at the beginning of certain endodontic procedures (such as the openings80, 84, and 88; see FIGS. 6A-6C), rather than fitting over or around theexterior of the tooth 10.

As depicted in the partially exploded cross-section view shown in FIG.10B, the distal end 58 of the handpiece 50 may include one or morepressure sensors 124. As the cap 120 is urged onto a tooth (or into anopening in the tooth), the pressure sensor 124 provides a signal thatindicates when a sufficiently “tight” fit has been achieved. Thepressure sensor 124 may be electrically connected to the controller 52,and enables the jet 60 to operate only when the sensor senses contact. Asuitable audible, visible, and/or tactile signal may be output (e.g., bythe user interface 54 or by an output device on the handpiece 50) toindicate that the cap 120 is in position on the tooth 10.

The system may also include a distance sensor to indicate the distancebetween the distal end 58 of the handpiece 50 and a surface of the tooth10. The distance sensor may provide an audible, tactile, and/or visibleindication when the distal end 58 is at a suitable distance from thesurface for operation of the liquid jet 60 (e.g., not too close todamage the tooth and not too far for the jet to be ineffective). In oneembodiment, the distance sensor comprises a pair of optical elementsmounted on the handpiece and spaced from each other. Each opticalelement directs an optical beam that intersects the other beam apredetermined distance away from the handpiece 50. The operator of thehandpiece 50 can maneuver the handpiece 50 until the intersecting beamsilluminate a desired portion of the tooth 10 and then actuate the liquidjet 60. The optical elements may comprise light-emitting diodes (LEDs)and/or lasers. In some embodiments, more than two optical elements maybe used (e.g., to indicate a range of distances).

A person of ordinary skill will recognize that a wide variety of sensorsmay be used in addition to or instead of the pressure sensor 124 and/orthe distance sensor. For example, certain embodiments utilize one ormore electric, magnetic, acoustic, and/or optical sensors to determineposition and/or orientation of the handpiece 50 (or portions thereof) inthe mouth. For example, proximity sensors, including capacitive sensors,ultrasonic sensors, light reflectance sensors, magnetic inductancesensors, and so forth, may be used. Certain embodiments may comprise oneor more orientation sensors (e.g., accelerometers) configured to sensethe orientation of the longitudinal jet axis 70 relative to one or morereference landmarks in the mouth (e.g., a portion of the tooth 10 suchas the openings 80, 84, 88). The system may include a timer configuredto deactuate the jet 60 after a predetermined time interval to reducelikelihood of damage to the tooth 10 and/or root canal system. Systemscomprising one or more such sensors advantageously may provide increasedsafety. For example, certain such embodiments may prevent (or inhibit)an operator from actuating the liquid jet 60 until the distal end 58 ofthe handpiece 50 is suitably positioned and/or oriented adjacent thetooth 10.

As described herein, acoustic energy capable of producing cavitation maybe particularly effective at cleaning the root canal system. It has beenfound that this acoustic energy may be efficiently produced by directinga high-velocity beam of liquid onto a portion of the tooth. However, thescope of the present disclosure is not limited to methods usinghigh-velocity jets. In other embodiments, the acoustic energy isgenerated by vibrating mechanical devices (e.g., a piezoelectrictransducer), ultrasonic (or megasonic) generators (e.g., an ultrasonicand/or a megasonic horn), or any other component capable of producingacoustic vibrations. FIG. 11 schematically illustrates one method forgenerating the acoustic wave 100 using a piezoelectric transducer 144.In this method, an enclosure 142 is attached to the tooth 10. Theenclosure 142 comprises a chamber 140 filled with a liquid (e.g.,water). The transducer 144 is disposed in or on the chamber 140. Whenactuated, the transducer 144 vibrates, which causes the acoustic wave100 to propagate through the surrounding fluid and the tooth 10. Theacoustic wave 100 cleans the root canal system substantially asdescribed above. Because the vibrating transducer 144 is not in directcontact with the tooth 10, possible damage to the tooth 10 is reduced oreliminated. Although in FIG. 11 a mechanical transducer 144 is used togenerate the acoustic wave 100, in other embodiments, the acoustic wave100 may be produced by, for example, directing the high-velocity liquidjet into or onto the enclosure 142. In such embodiments, the enclosure142 acts as an “acoustic waveguide” converting jet kinetic energy intoacoustic energy that propagates through the tooth 10 as the acousticwave 100. Beneficially, the liquid in the chamber 140 may absorb excessmechanical energy which may otherwise produce unwanted heat in the tooth10. In another embodiment, an ultrasonic horn is disposed near theenclosure 142 and used to generate the acoustic wave 100.

Any of the procedures described herein may be carried out with the useof a rubber dam. Further although the tooth 10 depicted in the figuresis a molar, one of ordinary skill in the art will appreciate that theprocedures may be performed on any type of tooth such as an incisor, acanine, a bicuspid, or a molar. Also, the disclosed methods are capableof cleaning root canal spaces having a wide range of morphologies,including highly curved root canal spaces which are difficult to cleanusing conventional dental techniques. Moreover, the disclosed methodsmay be performed on human teeth (including children's teeth) and/or onanimal teeth.

The foregoing description sets forth various preferred embodiments andother illustrative but non-limiting embodiments of the inventionsdisclosed herein. The description provides details regardingcombinations, modes, and uses of the disclosed inventions. Othervariations, combinations, modifications, equivalents, modes, uses,implementations, and/or applications of the disclosed features andaspects of the embodiments are also within the scope of this disclosure,including those that become apparent to those of skill in the art uponreading this specification. Additionally, certain objects and advantagesof the inventions are described herein. It is to be understood that notnecessarily all such objects or advantages may be achieved in anyparticular embodiment. Thus, for example, those skilled in the art willrecognize that the inventions may be embodied or carried out in a mannerthat achieves or optimizes one advantage or group of advantages astaught herein without necessarily achieving other objects or advantagesas may be taught or suggested herein. Also, in any method or processdisclosed herein, the acts or operations making up the method/processmay be performed in any suitable sequence and are not necessarilylimited to any particular disclosed sequence.

Accordingly, the scope of the inventions disclosed herein is to bedetermined according to the following claims and their equivalents.

What is claimed is:
 1. A method for treating an infected or decayingcondition in a tooth, the method comprising: providing a liquid mediumat a treatment region of the tooth including the infected or decayingcondition, wherein providing a liquid medium at the treatment regioncomprises supplying a substantially degassed liquid; generating a pulsedcoherent energy beam with a pressure wave generator; directing thepulsed coherent energy beam into the liquid medium present at thetreatment region of the tooth; and generating pressure waves within theliquid medium to remove infected or decaying material from the tooth atthe treatment region.
 2. The method of claim 1, further comprisinggenerating pressure waves of sufficient energy to remove infected ordecaying material from the tooth throughout the treatment region,including at locations remote from the portion of the treatment regionat which the pulsed coherent energy beam is directed.
 3. The method ofclaim 1, additionally comprising directing the pulsed coherent energybeam against a surface in the tooth.
 4. The method of claim 1,additionally comprising generating pressure waves of sufficient energyto create surface-effect cavitation at an infected or decaying surfaceof the tooth.
 5. The method of claim 1, wherein generating a pulsedcoherent energy beam comprises activating a liquid jet device to producea collimated, coherent liquid jet and varying the liquid pressure withinthe liquid jet device.
 6. The method of claim 5 additionally comprisingactivating a pump to pressurize the liquid that forms the liquid jet. 7.The method of claim 6, wherein a pressure of the liquid that forms theliquid jet is in a range from about 2,000 psi to about 11,000 psi. 8.The method of claim 1, wherein the generated pressure waves comprisefrequencies within a widespread range of acoustic noise.
 9. The methodof claim 8, wherein the frequencies comprise frequencies in a range fromabout 1 Hz to about 10 MHz.
 10. The method of claim 1, wherein thepulsed coherent energy beam has a pulse frequency in a range from about0.1 Hz to about 10 MHz.
 11. The method of claim 1, additionallycomprising removing organic material from a root canal of the toothwithout directing the coherent energy beam down the root canal.
 12. Themethod of claim 11, wherein removing organic material comprises removingsubstantially all organic material from lateral canal branches.
 13. Themethod of claim 1, additionally comprising applying a cap to the tooth,the cap disposed about the pressure wave generator.
 14. The method ofclaim 1, additionally comprising removing fluid from the treatmentregion through a suction port.
 15. A method for treating an infected ordecaying condition in a tooth, the method comprising: supplying fluid toa treatment region of the tooth including the infected or decayingcondition in the tooth wherein supplying fluid comprises supplying asubstantially degassed liquid; and directing a coherent energy beam intothe supplied fluid to generate pressure waves through the fluid, thegenerated pressure waves being sufficient to treat the infected ordecaying condition.
 16. The method of claim 15, further comprisingdirecting the coherent energy beam into the supplied fluid at a portionof the treatment region to generate pressure waves through the fluid,the generated pressure waves having sufficient energy to remove infectedor decaying material throughout the treatment region, including atlocations remote from the portion of the treatment region at which thecoherent energy beam is directed.
 17. The method of claim 15,additionally comprising generating a pulsed coherent energy beam. 18.The method of claim 15, additionally comprising generating pressurewaves of sufficient energy to create surface-effect cavitation at aninfected or decaying surface of the tooth.
 19. The method of claim 15,further comprising directing the coherent energy beam against a surfacein the tooth.
 20. The method of claim 15 additionally comprisingavoiding directing the coherent energy beam down a root canal of thetooth while directing the coherent energy beam into the supplied fluid.